Polymers find uses in a variety of plastic articles including films, sheets, fibers, foams, molded articles, adhesives and many other specialty products. The majority of this plastic material ends up in the solid waste stream. While some efforts at recycling have been made, repeated processing of even pure polymers results in degradation of material and consequently poor mechanical properties. Different grades of chemically similar plastics mixed upon collection can cause processing problems that make the reclaimed material inferior or unusable. Thus, there is a need for plastic articles which are biodegradable.
There is also a need for articles which are non-latex-allergenic. Latex rubber is formed from latex, which is the milky sap of the commercial rubber tree, Hevea Brasiliensis. Latex rubber contains proteins, including enzymes which are involved in the biosyntheses of rubber molecules such as polymers of (cis-1,4-polyisoprene), and chemicals added during the preparation of the rubber, such as accelerators and antioxidants. Unfortunately, some individuals are allergenic to products comprising latex rubber. Such latex allergies include syndromes such as chemical irritation dermatitis; a T-cell mediated response causing localized reaction, referred to as type 4 delayed hypersensitivity or allergenic contact dermatitis; immediate type hypersensitivity or urticaria; and anaphylactic reaction, also referred to as type 1 hypersensitivity, mediated by IgE antibodies. Individuals at risk for developing latex allergies are those with prolonged or frequent exposure to latex products, particularly patients with neural tube defects, such as spinal bifida and congenital urologic abnormalities, as well as health care workers with chronic exposure to latex, particularly latex gloves. Thus, there is a need for methods of reducing latex exposure.
Additionally, soft plastics, such as vinyls, may comprise plasticizers, such as phthalates, or heavy metals, such as lead and cadmium. The phthalate plasticizers are used to obtain a flexible plastic, while the heavy metal are used to decrease degradation. As there is concern that plasticizers and heavy metals may leach from items such as baby teethers, nipples, intravenous tubing and vinyl food wrap, it is desirable to provide methods of reducing exposure to plasticizers and heavy metals.
Spencer, U.S. Pat. No. 5,733,268, discloses medical tubing and containers comprising an ionomeric modified poly-ether-ester plastic material combined with small amounts of a polyvinylchloride. Spencer teaches that the poly-ether-ester is plasticizer-free. Spencer further teaches items such as peritoneal dialysis assemblies, urinary drainage assemblies, chemotherapy assemblies, parenteral feeding assemblies and food processing assemblies comprising such tubing.
Sinclair et al., U.S. Pat. No. 5,760,118, disclose products comprising a hydrolytically degradable polymer. Sinclair et al. teach products such as adhesive tapes, medical disposal bags, film wrap, gloves, mask, disposable clothing and bedding products for hospitals, dental floss, toothbrushes, thermometer mouth pieces, syringes, micropipet tips, shavers, support for cotton swabs, contact lenses, intravenous tubing, catheter tubing, needles, syringes, bags for fluids such as blood and plasma, and supports for growing living cells. Sinclair et al. further teach items such as toys, containers, mulches, seed tapes and absorbent items.
Holmes, U.S. Pat. No. 4,620,999, teaches disposable bags for body-waste comprising a 3-hydroxybutyrate polymer and a basic material to modify the pH of the bag contents to a pH of at least about 12.
Noda, U.S. Pat. No. 5,918,747, discloses a process for recovering polyhydroxyalkanoates from biological sources. Noda further teaches the polyhydroxyalkanoates can be used to form disposable health care products such as bandages, wound dressings, wound cleansing pads, surgical gowns, surgical covers, surgical pads and bedding items such as sheets, pillowcases and foam mattress pads.
Asrar et al., WO 99/04948, disclose methods of producing coated objects comprising melting a polyhydroxyalkanote, such as polyhydroxybutyrate or polyhydroxy-butyrate-co-valerate, and extrusion coating the object. Asrar et al. teach the coating has a molecular weight of greater than 125,000 daltons.
There is a continuing need for methods of reducing exposure to latex and to plasticizers. There is a need for biodegradable items which are substantially free of latex, particularly items which come in contact with an individual's body or component thereof. As used herein “body components” refers to organs or bodily parts, such as skin, mucous membranes or eyes. It is desirable that items which a child may put in his mouth, such as teethers and nipples, be free of latex. Preferably, such items are further free of plasticizers and heavy metals.
Unfortunately, many biodegradable items are brittle, or are incapable of degrading under both aerobic and anaerobic conditions. Further, prior art polymers such as polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate often have unsatisfactory properties. Polyhydroxybutyrate tends to be thermally unstable, while polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate often have slow crystallization rates and flow properties which make processing difficult. For example, polyhydroxybutyrate-co-hydroxyvalerate remains tacky for long periods of time, and may stick to itself when being processed into films.